https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63139
Bug ID: 63139
Summary: Class-scope typedef overwrites typedef of previously
defined class
Product: gcc
Version: 4.9.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: david.d.kretzmer at gmail dot com
In GCC 4.8 and 4.9 (4.7 seems to work correctly) a type alias inside a class
seems to overwrite under certain conditions a type alias of the same name in a
previously defined class.
Code to reproduce this bug:
------------------------------------------------------------
#include <type_traits>
template<typename ...T>
struct type_list {};
template<typename ...T>
struct make_type_list
{
using type = type_list<T...>;
};
// The bug disappears if you use make_type_list directly.
template<typename ...T>
using make_type_list_t = typename make_type_list<T...>::type;
struct ContainerEndA {};
template<typename ...Ts>
struct ContainerA
{
using type = make_type_list_t<Ts..., ContainerEndA>;
};
struct ContainerEndB {};
//template<typename Head, typename ...Lists> // If you use this line instead
of the next a Internal compiler error is generated.
template<typename ...Ts>
struct ContainerB
{
using type = make_type_list_t<Ts..., ContainerEndB>;
};
int main()
{
// To see the types in ContainerA<>::type uncomment the following line.
//
//ContainerA<>::type::doesnt_exist;
//
// GCC error: ‘doesnt_exist’ is not a member of ‘ContainerA<>::type {aka
type_list<ContainerEndB>}’.
// So according to GCC ContainerA<>::type contains ContainerEndB, but it
clearly contains only ContainerEndB!
static_assert(
// It doesn't matter which types you use to instantiate ContainerA and
ContainerB
std::is_same<ContainerA<int>::type, ContainerB<int>::type>::value,
"This assert doesn't fail but it clearly should!"
);
}
------------------------------------------------------------
I have tried to minimize the code further but any time I remove something the
bug disappears.
